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Regression with narrowing with multiple hasattr #20596
Description
[case testMultipleHasAttr]
# flags: --warn-unreachable
from __future__ import annotations
from typing import Any
def len(obj: object) -> Any: ...
def f(x: type | str):
if (
hasattr(x, "__origin__")
and x.__origin__ is list
and hasattr(x, "__args__")
and len(x.__args__) == 1
):
reveal_type(x.__args__[0]) # N: Revealed type is "Any"
[builtins fixtures/module.pyi]
Regression introduced in #20492 that I don't yet have fixed in my commit stack. Probably just need to manage the conditional type maps a little more carefully
Activity
Fix regression with narrowing and multiple hasattr checks (issue pyth…
James-4u commentedon Jan 20, 2026
hello @hauntsaninja requesting your reviews 😄
https://github.com/python/mypy/compare/master...SmartDever02:fix-issue-20596-hasattr-narrowing?expand=1
hauntsaninja commentedon Jan 29, 2026
I have a patch that fixes this that does some reordering of how things get set in the output_map in
propagate_up_typemap_info... but it doesn't feel principled and I don't like itMaybe if I can clean up some more type map logic a better fix will reveal itself
Correctly aggregate narrowing information on parent expressions (pyth…
Correctly aggregate narrowing information on parent expressions (#21206)